Magnetic resonance imaging (MRI) is a bio-magnetic nuclear spin imaging technology developed rapidly along with the development of computer technology, electronic circuit technology, and superconductor technology. MRI utilizes a magnetic field and a radio frequency pulse to cause the moving hydrogen nuclei (i.e., H+) within the human tissue to vibrate so as to generate radio frequency signals that are processed by a computer to form an image. When an object is placed in the magnetic field, appropriate electromagnetic waves are irradiated thereon to make the object resonate. Electromagnetic waves released therefrom are then analyzed. Thus, the locations and types of the atomic nuclei that constitute this object may be learned, and based on this, an accurate stereoscopic image of the interior of the object may be drawn. For example, an animation with consecutive slices from the top of the head down to the feet may be obtained by scanning the human brain using magnetic resonance imaging.
In an MRI system, a transmitting antenna level sensor (TALES) is an accurate radio frequency signal voltmeter for measuring a forward and a backward power of a transmitting coil. For example, in CN1823684A, a magnetic resonance tomography imaging system and a high frequency control system are disclosed. The high frequency control system adopts a TALES to measure a forward power that is sent to a high frequency antenna by a sending device and a backward power that is returned by the high frequency antenna.
The TALES is prone to various failures such as ageing after long term usage, thus causing the measurement value to drift from the actual value. In the prior art, in order to overcome various defects caused by the drift error, the TALES is regularly returned to the factory for inspection. However, such a processing method significantly increases various types of costs, and may not find failures promptly when drifts occur.